Field of the Invention
The present invention relates to a tunnel boring device used in the excavation of a tunnel, and to a method for controlling this device.
Description of the Related Art
The excavation of a tunnel is performed using a boring machine equipped with a cutter head including a cutter at the front of the machine, and grippers provided on the left and right sides at the rear of the machine.
This boring machine excavates the tunnel by pressing the rotating cutter head against the working face in a state in which the left and right grippers have been pressed against the left and right side walls of the tunnel.
Japanese Laid-Open Patent Application S61-266797, for example, discloses a method for the directional control of an underground excavator, comprising a forward section having a cutter that performs rock excavation, and a rear section that has grippers for producing a counterforce for excavation, and that is linked via an actuator, etc., to the forward section.
With this underground boring machine, actuators (such as thrust jacks) are installed to allow bending between the forward section and the rear section, which makes the excavation of a curved tunnel possible.
Also, with the underground boring machine disclosed in Japanese Laid-Open Patent Application S61-266797, the operator has to adjust the attitude of the forward section by varying the stroke of the thrust jacks as needed, so that the excavated tunnel will not deviate from a stored planned excavation line even if the excavation is performed automatically on the basis of the planned excavation line and the direction in which the underground boring machine moves ends up changing due to a change in the hardness of rocks, etc.
Since the position and direction of the forward section require the three X, Y, and Z axes of a perpendicular coordinate system and movement with six degrees of freedom in the rotation of these axes, a six-axis drive link is necessary.
With one type of six-axis drive link, the rod side of six thrust jacks is linked to the forward section, and the cylinder tube side is linked to the rear section. A six-axis drive link such as this employs a so-called parallel link structure, in which the rod sides of a plurality of thrust jacks are disposed annularly near the outer peripheral edge of a face of the forward section that is opposite the forward section.